Cardiac arrest

Main mechanisms

From an electrophysiological perspective, two very different situations can cause cardiac arrest:

• Ventricular fibrillation (VF): a severe arrhythmia characterized by rapid, irregular, and unsynchronized contractions of the ventricles. The heart “quivers” chaotically, unable to pump blood effectively. It is the equivalent of a cardiac “electrical storm.” VF is responsible for about 75 to 80% of out-of-hospital cardiac arrests in adults;
• Asystole: corresponds to the complete absence of cardiac electrical activity, seen as a flat line on the electrocardiogram. This is commonly referred to as a “flatline.” In this situation, the heart is completely stopped;
• Pulseless electrical activity (PEA): a situation in which cardiac electrical activity is visible on the monitor, but no effective mechanical contraction is generated, meaning no palpable pulse is produced.

It is essential to distinguish between these mechanisms because their management differs. In particular, only ventricular fibrillation and pulseless ventricular tachycardia can be treated with an electric shock (defibrillation), whereas defibrillation is ineffective in cases of asystole or PEA.

Underlying causes

The causes of cardiac arrest are numerous and can be grouped into several categories:

• Cardiac causes:
  • Ischemic heart disease (acute myocardial infarction or post-infarction damage): the leading cause of cardiac arrest in adults;
  • Cardiomyopathies (dilated, hypertrophic, arrhythmogenic right ventricular cardiomyopathy);
  • Severe ventricular rhythm disorders (Brugada syndrome, long QT syndrome);
  • Severe conduction disorders (high-degree atrioventricular blocks);
  • Cardiac tamponade (compression of the heart by pericardial effusion);
  • Acute myocarditis.
• Respiratory causes:
  • Acute asphyxia (foreign body, drowning, hanging);
  • Massive pulmonary embolism;
  • Tension pneumothorax;
  • End-stage respiratory failure.
• Metabolic and toxic causes:
  • Severe electrolyte disturbances (hyperkalemia, hypokalemia);
  • Drug poisoning (antiarrhythmics, psychotropic drugs);
  • Drug intoxication (cocaine, amphetamines);
  • Severe hypothermia.
• Neurological causes:
  • Massive stroke;
  • Severe subarachnoid hemorrhage.
• Traumatic causes:
  • Severe chest trauma;
  • Massive hemorrhage;
  • Electric shock/electrocution.

A complete evaluation by an electrophysiologist is recommended for survivors of cardiac arrest to identify the underlying cause and implement appropriate secondary prevention. This evaluation can be performed at Institut Mutualiste Montsouris (Paris 14th), where the electrophysiologists at Rythmopôle Paris have access to dedicated technical facilities.

Cardiac arrest is characterized by a sudden onset without warning signs in about 50% of cases. However, in the hours or minutes preceding the event, certain signs may sometimes be observed:

• Prodromes (warning signs):
  • Chest pain (in the case of an underlying myocardial infarction);
  • Palpitations;
  • General malaise, feeling of intense weakness;
  • Sudden shortness of breath;
  • Cold sweats, nausea;
  • Unexplained anxiety, feeling of impending death.

At the moment of cardiac arrest, the manifestations are characteristic and allow for immediate diagnosis:

• Clinical signs:
  • Sudden loss of consciousness;
  • No response to stimulation (unconsciousness);
  • Absence of breathing or agonal breathing (gasps);
  • Absence of central pulse (carotid or femoral);
  • In 10 to 20% of cases, brief convulsions may be observed due to cerebral hypoxia.

At-risk populations

Certain populations have an increased risk of cardiac arrest:

• Patients with known ischemic heart disease;
• Patients with heart failure and a low left ventricular ejection fraction (< 35%);
• Family history of early sudden death (< 45 years);
• Carriers of genetic mutations associated with cardiac rhythm disorders (long QT syndrome, Brugada syndrome, hypertro
  

Diagnosis of cardiac arrest

The diagnosis of cardiac arrest is based on the rapid identification of characteristic clinical signs:

• The victim does not respond when spoken to or stimulated;
• The victim is not breathing normally (absence of breathing or abnormal “gasping” respiration);
• For healthcare professionals only: absence of carotid or femoral pulse (pulse checking is no longer recommended for the general public due to its difficulty and the risk of delaying chest compressions).

If in doubt, it is recommended to assume cardiac arrest and immediately begin cardiopulmonary resuscitation (CPR).

Immediate management

The management of cardiac arrest follows the chain of survival, which includes four key links:

1. Early alert: immediately call the emergency services (15, 18, or 112);
2. Early cardiopulmonary resuscitation (CPR):
   • Place the victim on a firm, flat surface and expose the chest;
   • Perform chest compressions in the center of the chest at a rate of 100–120 per minute and a depth of 5–6 cm;
   • For trained responders: alternate 30 chest compressions with 2 rescue breaths. For untrained responders: perform chest compressions only, without interruption;
   • Continue until help arrives or the rescuer is exhausted. If multiple rescuers are present, switch every 2 minutes to maintain compression quality.
3. Early defibrillation:
   • Use an automated external defibrillator (AED) as soon as it is available;
   • Turn on the device and follow the voice instructions;
   • Place the pads as shown on the victim’s bare, dry chest;
   • Ensure no one is touching the victim during rhythm analysis and shock delivery if indicated;
   • Immediately resume chest compressions after the shock.
4. Advanced medical care: upon arrival of advanced medical teams (SAMU, SMUR), advanced resuscitation techniques are initiated:
   • Intubation and mechanical ventilation;
   • Vascular access and administration of medications (adrenaline, amiodarone);
   • Manual defibrillation;
   • Treatment of reversible causes;
   • Transport to a specialized hospital center.

Hospital and post-resuscitation management

After initial resuscitation and return of spontaneous circulation, hospital care aims to:

• Stabilize the patient’s hemodynamic status;
• Identify and treat the underlying cause of cardiac arrest (emergency coronary angiography if myocardial infarction is suspected);
• Implement neuroprotective measures (targeted temperature management);
• Prevent and treat secondary organ failure;
• Assess neurological prognosis.

Once the patient is stabilized, a complete cardiology evaluation is performed by electrophysiologists to determine the exact cause and implement an appropriate secondary prevention strategy, which may include the implantation of an implantable cardioverter-defibrillator (ICD) in certain cases.

This evaluation and the implantation of such devices are carried out at Institut Mutualiste Montsouris by the electrophysiologists of Rythmopôle Paris.

Primary prevention

Primary prevention aims to avoid the occurrence of a first cardiac arrest in at-risk individuals:

• Screening and treatment of cardiovascular risk factors:
  • High blood pressure;
  • Diabetes;
  • Dyslipidemia;
  • Smoking;
  • Obesity, sedentary lifestyle.
• Diagnosis and treatment of heart diseases:
  • Optimal management of coronary artery disease;
  • Medical treatment of heart failure;
  • Correction of severe valvular disease.
• Screening for inherited rhythm disorders in at-risk families (cardio-genetic consultation).
• Implantation of an implantable cardioverter-defibrillator (ICD) as primary prevention in certain high-risk patients:
  • Patients with severe left ventricular dysfunction (LVEF ≤ 35%) despite optimal medical therapy;
  • Certain hypertrophic or arrhythmogenic right ventricular cardiomyopathies;
  • High-risk genetic rhythm syndromes (Brugada syndrome, long QT syndrome, etc.).

These preventive assessments can be carried out in the various Rythmopôle Paris centers, particularly at Centre Cœur et Santé Bernouilli (Paris 8th) and Cardiopôle Yvart (Paris 15th).

Secondary prevention

Secondary prevention concerns survivors of cardiac arrest and aims to prevent recurrence:

• Implantation of an implantable cardioverter-defibrillator (ICD): recommended for the vast majority of cardiac arrest survivors whose cause is not fully reversible;
• Treatment of the underlying cause:
  • Coronary revascularization in cases of ischemic heart disease;
  • Optimal medical treatment of heart failure;
  • Complementary antiarrhythmic therapy in certain cases.
• Regular electrophysiology follow-up with ICD checks and treatment adjustments.
• Education of the patient and their family on warning signs and emergency measures.

ICD implantation and follow-up are performed at Institut Mutualiste Montsouris, and follow-up can be provided in several Rythmopôle Paris centers, including Cardiopôle Peupliers-Trubert.

Public awareness and training

Preventing deaths from cardiac arrest also involves training the general public in life-saving measures:

• Training in first aid (PSC1);
• Learning how to use automated external defibrillators (AEDs);
• Installing AEDs in public places and raising awareness of their presence;
• Developing mobile applications to locate AEDs and alert nearby volunteer responders.

Life-saving training sessions are regularly organized by various associations (Red Cross, Civil Protection, etc.), and some are also offered as part of awareness campaigns by the teams at Rythmopôle Paris.

Sequelae and rehabilitation

Patients resuscitated after cardiac arrest require specific management:

• Neurological assessment: anoxic brain injury, present in about 30–50% of survivors, can range from mild cognitive impairment to severe neurological deficits. Specific neurological rehabilitation is often necessary;
• Psychological support: post-traumatic stress disorder, anxiety, and depression are common complications requiring appropriate care;
• Cardiovascular rehabilitation: essential to optimize functional recovery, it is offered at Cardiopôle Yvart, where a personalized program can be developed.

Follow-up for patients with an implantable defibrillator

The majority of cardiac arrest survivors receive an implantable cardioverter-defibrillator (ICD):

• Monitoring consultations: regular ICD check-ups (every 3 to 6 months) and the possibility of remote monitoring for early detection of anomalies or arrhythmias;
• Optimization of settings: customization of device detection and therapy parameters to minimize inappropriate shocks;
• Therapeutic adaptation: regular adjustment of drug treatments in addition to the ICD;
• Therapeutic education: information on precautions to take (electromagnetic environments, permitted physical activities) and what to do in case of a shock.

This specialized follow-up is provided in several Rythmopôle Paris centers, with particular attention paid to optimizing device settings and preventing complications.

Rythmopôle Paris offers comprehensive expertise in the management of patients who have experienced cardiac arrest or are at risk of this complication:

• A team of experienced electrophysiologists specializing in the diagnosis and treatment of life-threatening heart rhythm disorders;
• Fully equipped technical facilities at Institut Mutualiste Montsouris for performing all necessary post–cardiac arrest assessments (coronary angiography, cardiac MRI, cardiac CT scan, electrophysiological study);
• Expertise in the implantation and programming of implantable cardioverter-defibrillators (ICDs);
• A tailored cardiac rehabilitation program for cardiac arrest survivors at Cardiopôle Yvart;
• Personalized follow-up with implantable device checks in several centers across the Île-de-France region;
• A multidisciplinary approach involving cardiologists, electrophysiologists, neurologists, and psychologists for comprehensive care;
• Expertise in cardio-genetics for family screening in cases of suspected hereditary conditions.